40 years and 1,500 feet apart: Two Madison home explosions, but no likely connection

1983 Greentree Landfill explosion on intersection of S. Gammon and Hammersley roads

A witness who spoke to News 3 Now at the time described seeing the side of the building in the street, with a man blown through the wall and left burned with his hair singed off.

"The girl was just standing upstairs where the wall isn't, she was just standing, shaking and screaming upstairs there," the witness said.

The explosion in November 1983 left both people with severe burns and destroyed the building. Ed Durkin, Madison's fire chief at the time, said methane levels were also found at explosive levels in the home next door to the one that exploded.

"It was a lot of power; an amazing amount of power," Marcie Holm recalled, speaking with News 3 Investigates on Wednesday. She and her husband had lived near the site of the explosion that day; it would ultimately drive them to move to another part of Madison shortly after before leaving Madison for good in 2011.

"You're waiting for something to happen at any time," Holm said, describing how they felt after officials identified methane as the explosion's cause. "My husband was a smoker, which made it twice as bad. Every time you light a match, you're wondering, 'Is this going to be a replay of what just happened?'"

The explosion would ultimately be blamed on the Greentree Landfill, where methane gas had leaked from the closed landfill into nearby apartments and risen to levels that exploded when a resident lit a pipe. The incident launched lawsuits and investigations, leading to the city taking substantive measures to study and control methane gas as well as contaminated water generated by leaking pollutants from landfills across the city.

Hundreds of homeowners were left worried about diminished home values and the extensive damage, retired city engineer and environmental manager Dave Benzschawel told News 3 Investigates on Wednesday.

"The landfill was like a pressure cooker with the lid on it," Benzschawel recalled. All of the lawsuits were settled out of court, he said, so it has never been ascertained in a court of law whether the city, the barometric pressure conditions, or building owners and contractors had some responsibility.

But going forward, it led to at least $100 million in city funds directed into old landfill cleanups.

City, former engineer say connection between 1983, 2023 explosions unlikely

City engineering staff cited a few reasons why a connection is unlikely between the two incidents, with the first being the simplest: the condo from Tuesday night's explosion is roughly 1500 feet from the landfill's northern boundaries, while the home in 1983 sat nearly on top of it.

The second reason is a bit more complicated, and stems from improvements put in place after the 1983 explosion, city staff explained.

The city of Madison operated the landfill from 1973 to 1980. After the 1983 explosion following its closure, the city put a gas extraction system in place that operates continuously to apply a vacuum over the entire landfill that creates an inward pressure gradient underground, city engineer Jack Brody told News 3 Investigates.

The system essentially sucks out the gas created by decomposing waste and prevents it from migrating away from the landfill.

Additionally, the city takes weekly gas readings from 20 probes surrounding the limits of the landfill; five of those probes are checked twice weekly, Brody said.

Since 2021 when the system was updated, the city has not detected methane gas in the area of the Greentree Landfill.

The 2021 update was the latest in a series of system upgrades and protections that city staff put in place after the explosion. In 1984, Brody said the city expanded its gas monitoring network and installed the full-perimeter landfill gas control system. Ten years later, the city upgraded it again with the interior gas extraction system, with the Wisconsin Department of Natural Resources approving a final cover system for the landfill that would also isolate the waste from the environment.

City engineering has 'no reason to believe' landfill is a factor for 2023 explosion

A spokesperson for the Madison Fire Department told News 3 Investigates on Wednesday morning that they didn't have any information at this stage of the investigation about the landfill as a possible cause.

Brody said that city engineering hadn't been contacted in regards to the investigation as of early Wednesday afternoon, a sign that the landfill is unlikely a factor.

More significantly, city staff checked the methane gas probes surrounding the landfill on Wednesday morning after the explosion, and the two probes nearest the explosion both showed no methane present.

"This means that the underground soils northwest of the landfill are under the influence of the active gas extraction system," Brody wrote. "Any subsurface gas in this locality would be pulled toward the landfill gas extraction system and not pushed outward away from the landfill."

The risk level to nearby residents is now "pretty much nonexistent," Benzschawel said on Wednesday. The system, he said, is replete with overlapping protections: alarms were installed to go off if methane levels crept up, and staff check the system constantly regardless of severe weather conditions.

Meanwhile, Madison Fire's investigation into Tuesday night's explosion continues. While some residents and witnesses told News 3 Now they had smelled gas prior to the explosion, Madison Gas and Electric said on Wednesday that they were on scene in the aftermath and there was no evidence that a gas leak had happened. As of Wednesday evening, fire officials say a propane source in the condo's garage may be to blame.

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